ZmtLaunchPlugin.java: no longer uses deprecated methods

src/main/groovy/de/zmt/gradle/ZmtLaunchPlugin.groovy

@@ -94,10 +94,10 @@ public class ZmtLaunchPlugin implements Plugin<Project> {
         
         run {
             description = description + ". Arguments can be supplied via 'args' project property (-Pargs='<args>')."
-            if (project.has('args')) {
+            if (project.hasProperty('args')) {
                 args(project.args.split())
             }
-            if (project.has('workingDir')) {
+            if (project.hasProperty('workingDir')) {
                 workingDir = project.workingDir
             }
         }